The trend in the semiconductor industry today is the production of ever increasingly more capable semiconductor components, while decreasing component size and total semiconductor package height. In other words, increased semiconductor chip density. The production of such semiconductor devices reveals new and challenging design and manufacturing problems. Such problems are seen in deep sub-micron fabrication techniques, where denser chip designs and shorter turn-around time requirements can lead to quality control issues. These quality control issues include possible silicon failure and the resultant re-masking, thereby increasing production costs.
Printed circuit boards, such as sub-micron layout designs, make use of vertical electrical inter-connections, or vias. Vias as well as other forms of electrical contacts provide electrical connection between different metal layers of a printed circuit board.
Defects associated with these vias may contribute to yield loss. These defects can be categorized into three areas: random defects, systematic defects, and parametric defects.
Random defects (e.g., particle defects) are those defects caused by by-products of the manufacturing process itself. Manufacturing defects would include, for example, an airborne particle, or more likely, a particle that breaks off during polishing. If such a particle lands on or near a via, it can block that via from functioning properly.
Systematic defects (e.g., pattern dependencies in the layout) are those defects associated with particular design patterns or layouts. For example, when copper was introduced in the manufacturing process, air bubbles became a problem because they have a tendency to accumulate at areas of stress, such as a via insertion point. Such areas of stress from the manufacturing process caused by the layout patterns can void a via.
Parametric defects (e.g., timing related issues) are those defects resulting from interconnection parasitic effects and device physics. For example, when a via becomes partially blocked, it produces a greater resistance (called a resistive via), and its performance is thereafter inhibited.